Alumina coating on dense tungsten powder by fluidized bed metal organic chemical vapour deposition

In order to study the feasibility of coating very dense powders by alumina using Fluidized Bed Metal Organic Chemical Vapour Deposition (FB-MOCVD), experiments were performed on a commercial tungsten powder, 75 microm in median volume diameter and 19,300 kg/m3 in grain density. The first part of the work was dedicated to the experimental study of the tungsten powder fluidization using argon as carrier gas at room temperature and at 400 degrees C. Due to the very high density of the tungsten powder, leading to low initial fixed bed heights and low bed expansions, different weights of powder were tested in order to reach satisfactory temperature profiles along the fluidized bed. Then, using argon as a fluidized bed former and aluminium acetylacetonate Al(C5O2H7)3 as a single source precursor, alumina thin films were deposited on tungsten particles at a low temperature range (e.g., 370-420 degrees C) by FB-MOCVD. The influence of the weight of powder, bed temperature and run duration was studied. Characterizations of the obtained samples were performed by various techniques including scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) analyses, Field Emission Gun SEM (FEG-SEM) and Fourier Transform InfraRed (FT-IR) spectroscopy. The different analyses indicated that tungsten particles were uniformly coated by a continuous alumina thin film. The thickness of the film ranged between 25 and 80 nm, depending on the coating conditions. The alumina thin films were amorphous and contained carbon contamination. This latter may correspond to the adsorption of species resulting from incomplete decomposition of the precursor at so low deposition temperature.     

Biomass production and small-scale testing of freeze-dried lactic acid bacteria starter strains for cassava fermentations

Based on their predominance in Gari fermentations, as well as suitable technological properties, Lactobacillus plantarum, Lactobacillus fermentum, Weissella paramesenteroides and Leuconostoc mesenteroides strains were investigated for their suitability for development as starter strains for this African traditional fermented cassava product. The strains were grown in optimized growth media in 2 L fermenters, harvested and freeze dried, and then tested in lab-scale cassava mash fermentation trials for their ability to ferment the cassava. The strains performed well and rapidly increased the titratable acidity from 1.1 to 1.3% at 24 h to 1.3–1.6% at 48 h. The benefit of including starter cultures was that it lowered the pH of the product much faster and to lower levels than in the uninoculated control fermentation. The results furthermore indicated that especially the L. plantarum-group strains could be produced as starter strains at low cost. Overall, the results of this study showed that starter strains could be easily and economically produced, and thus represent a feasible possibility for further development for application in the field.     

Photopolymerization of N,N-Didodecyl- N-methyl-N-ethylmethacrylate ammonium chloride,a reverse micelle forming surfactant

A detailed study of the photopolymerization of N,N-didodecylmethylethylmethacrylate ammonium chloride, a reverse micelle forming surfactant, is presented. The polymerization was photochemically initiated at 350 nm using AIBN and p-AIBN as initiators. However, the polymerization could also be initiated through direct excitation of the methacrylate group. High rates of polymerization resulted because of the organization of the monomer in reverse micellar assemblies. The molecular weights of the polymer decrease with increasing initiator concentration and are always larger than the molecular weight of the reverse micelle. The properties of the monomeric reverse micellar system are compared with those of the polymeric system and show that the dynamic character of the reverse micellar system can be lowered upon polymerization. The properties of the polymeric aggregates, however, differ if a given amount of water is solubilized before or after polymerization. The mean aggregation number of the monomeric and polymeric aggregates as well as the aggregation behaviour of both systems are compared. This comparison suggests that a polymeric aggregate consists of more than one polymer chain.     

Stability of Protective Oxide Layer Against Corrosion: Solubility Measurements of Chromium in Soda Lime Silicate Melts

The solubility of chromium oxide (Cr₂O₃) in soda lime silicate glasses was studied as a function of temperature (1,200 °C ≤ T ≤ 1,350 °C), oxygen fugacity (?12 ≤ log fO₂ ≤ ?0.6) and glass composition (Na₂O–CaO–xSiO₂; x = 3, 4, 5 and 6). The fO₂ was proved to induce several oxidation states of Cr for a given glass composition at a fixed temperature. The influence of glass composition on the Cr solubility was interpreted in terms of the optical basicity Λ concept. An increase in the melt basicity led to an increase in the Cr solubility for the experiments conducted under oxidizing conditions. The total dissolved Cr also showed a significant increase with increasing temperature for a given fO₂ and glass composition. The results proved that the stability of Cr₂O₃ scale against corrosion was profoundly influenced by fO₂, T and melt basicity.     

Sex Dimorphism of Nonalcoholic Fatty Liver Disease (NAFLD) in Pparg-Null Mice

Men with nonalcoholic fatty liver disease (NAFLD) are more exposed to nonalcoholic steatohepatitis (NASH) and liver fibrosis than women. However, the underlying molecular mechanisms of NALFD sex dimorphism are unclear. We combined gene expression, histological and lipidomic analyses to systematically compare male and female liver steatosis. We characterized hepatosteatosis in three independent mouse models of NAFLD, ob/ob and lipodystrophic fat-specific (PpargF^Δ/Δ) and whole-body PPARγ-null (Pparg^Δ/Δ) mice. We identified a clear sex dimorphism occurring only in Pparg^Δ/Δ mice, with females showing macro- and microvesicular hepatosteatosis throughout their entire life, while males had fewer lipid droplets starting from 20 weeks. This sex dimorphism in hepatosteatosis was lost in gonadectomized Pparg^Δ/Δ mice. Lipidomics revealed hepatic accumulation of short and highly saturated TGs in females, while TGs were enriched in long and unsaturated hydrocarbon chains in males. Strikingly, sex-biased genes were particularly perturbed in both sexes, affecting lipid metabolism, drug metabolism, inflammatory and cellular stress response pathways. Most importantly, we found that the expression of key sex-biased genes was severely affected in all the NAFLD models we tested. Thus, hepatosteatosis strongly affects hepatic sex-biased gene expression. With NAFLD increasing in prevalence, this emphasizes the urgent need to specifically address the consequences of this deregulation in humans.     

Experience plan for controlled‐atmosphere cone calorimeter by Doehlert method

Controlled‐atmosphere cone calorimeter is an interesting test method to study at the same time the effect of oxygen concentration and radiant heat flux on materials' fire behaviour and gas release. However, measurements in an extended range for these two variables can be tedious. To optimize the experimental measurement, this paper proposes a methodology based on the Doehlert design. The Doehlert method allows significant optimization of the number of tests. The optimization of measurement response is then accomplished using polynomial approximations to establish fire behaviour constitutive. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermal degradation kinetics of a commercial epoxy resin—Comparative analysis of parameter estimation methods

The thermal degradation behavior of a commercial epoxy resin, EpoFix® (Struers), has been investigated by thermogravimetry (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) under nonisothermal conditions in an argon atmosphere. Different methods (Kissinger, Flynn–Wall–Ozawa (FWO), Friedman isoconversion methods, and nonlinear least‐squares (NLSQ) estimation method) have been used to analyze the thermal degradation process and determine the apparent kinetic parameters. The methods produce similar results in terms of activation energy estimations. Nevertheless, the NLSQ method has several advantages over the other methods in terms of both characterizing the activation energy and modeling the thermal degradation—i.e., including this model in a resin degradation process simulation. However, it is interesting to combine the NLSQ method with other isoconversion methods: they can reflect the dependence and variability of the activation energies during pyrolysis processes, while providing a good starting point for a nonlinear procedure, especially with respect to the activation energy E. This work is the first step (apparent kinetic reaction) of complete simulation of experimental oven of degradation of epoxy resin coating of impregnate nuclear fuel sample. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42201.     

Human IRP1 Translocates to the Nucleus in a Cell-Specific and Iron-Dependent Manner

Iron regulatory protein 1 (IRP1) is a bifunctional protein with mutually exclusive RNA-binding or enzymatic activities that depend on the presence of a 4Fe-4S cluster. While IRP1 is a well-established cytosolic protein, work in a Drosophila model suggested that it may also exhibit nuclear localization. Herein, we addressed whether mammalian IRP1 can likewise translocate to the nucleus. We utilized primary cells and tissues from wild type and Irp1^−/− mice, as well as human cell lines and tissue biopsy sections. IRP1 subcellular localization was analyzed by Western blotting, immunofluorescence and immunohistochemistry. We did not detect presence of nuclear IRP1 in wild type mouse embryonic fibroblasts (MEFs), primary hepatocytes or whole mouse liver. However, we observed IRP1-positive nuclei in human liver but not ovary sections. Biochemical fractionation studies revealed presence of IRP1 in the nucleus of human Huh7 and HepG2 hepatoma cells, but not HeLa cervical cancer cells. Importantly, nuclear IRP1 was only evident in iron-replete cells and disappeared following pharmacological iron chelation. These data provide the first experimental evidence for nuclear IRP1 expression in mammals, which appears to be species- and cell-specific. Furthermore, they suggest that the nuclear translocation of IRP1 is mediated by an iron-dependent mechanism.     

Methotrexate-Induced Liver Injury Is Associated with Oxidative Stress,Impaired Mitochondrial Respiration,and Endoplasmic Reticulum Stress In Vitro

Low-dose methotrexate (MTX) is a standard therapy for rheumatoid arthritis due to its low cost and efficacy. Despite these benefits, MTX has been reported to cause chronic drug-induced liver injury, namely liver fibrosis. The hallmark of liver fibrosis is excessive scarring of liver tissue, triggered by hepatocellular injury and subsequent activation of hepatic stellate cells (HSCs). However, little is known about the precise mechanisms through which MTX causes hepatocellular damage and activates HSCs. Here, we investigated the mechanisms leading to hepatocyte injury in HepaRG and used immortalized stellate cells (hTERT-HSC) to elucidate the mechanisms leading to HSC activation by exposing mono- and co-cultures of HepaRG and hTERT-HSC to MTX. The results showed that at least two mechanisms are involved in MTX-induced toxicity in HepaRG: (i) oxidative stress through depletion of glutathione (GSH) and (ii) impairment of cellular respiration in a GSH-independent manner. Furthermore, we measured increased levels of endoplasmic reticulum (ER) stress in activated HSC following MTX treatment. In conclusion, we established a human-relevant in vitro model to gain mechanistical insights into MTX-induced hepatotoxicity, linked oxidative stress in HepaRG to a GSH-dependent and -independent pathway, and hypothesize that not only oxidative stress in hepatocytes but also ER stress in HSCs contribute to MTX-induced activation of HSCs.